It’s not Mitt Romney or Newt Gingrich or Ron Paul. It’s Obama for America, the president’s re-election campaign, which badly wants to win this battleground state in November, as it did in 2008.

“The Republicans are here today, gone tomorrow,” said Obama volunteer Pat Walters, of Johnston, a suburb of Des Moines. “We’ve been doing this since 2009.”

Next Tuesday’s Republican caucus has dominated political conversations. Largely overlooked is that Obama is running unopposed in the Democratic caucus the same night.

It’s a dramatically different scene from four years ago, when Obama set his course for the White House by beating John Edwards and Hillary Rodham Clinton after months of intense campaigning in Iowa.

Obama can coast as far as this year’s nomination is concerned. But Iowa remains a general election swing state, and no one assumes his 9-point win here over John McCain in 2008 will give him a cushion next November.

Obama’s campaign never entirely left Iowa or several other competitive states, where he hopes relentless organizing can overcome a weak economy and his mixed record of fulfilling campaign pledges in the face of strong GOP opposition in Congress. If thousands of volunteers flocked to Obama’s 2008 campaign, this time he’s having to work a bit harder to recruit and energize them.

“People say, ‘The mood is different this time; it’s not the same,’” said Peggy Whitworth, an Obama volunteer in Cedar Rapids. “Well of course it’s not the same. But it’s not about mood or feeling. It’s about the future of the country.”

Whitworth, 69, said she joins other Obama volunteers four hours every Tuesday night, and sometimes on other evenings as well, to telephone potential supporters. Many say they will vote for Obama again, she said, and some volunteer to help the campaign. But some are disappointed or angry that the president fell short on campaign promises such as ending the Bush-era tax cuts for the wealthy, and bringing a greater spirit of bipartisanship to Washington.

“Sometimes they simply want to have someone listen to them,” Whitworth said. Most say they will stick with Obama after they’ve had a chance to vent their frustrations, she said.

Obama lacks some key advantages he enjoyed in 2008. They include a deeply unpopular GOP president who was largely blamed for a faltering economy, and a widespread excitement about Obama’s precedent-breaking campaign built on “hope and change.”

In exchange, of course, he has the power of the presidency and a well-oiled political organization that has been refining its practices for five years. Obama will raise many millions of dollars, although his eventual Republican opponent may do nearly as well.

Nowhere does Obama have a bigger base to build on than in Iowa, where he campaigned for months in 2007. Romney, Gingrich and other GOP contenders have not made comparable efforts, although they say the economy and other issues will make Obama’s task much harder next year.

In activities that rarely compete with the hoopla of the GOP nominating contest, Obama’s campaign has placed a handful of paid staffers in each of several key states. They try to leverage their clout by recruiting and training scores of volunteers. The volunteers, in turn, knock on doors, organize house parties and, above all, place phone calls to voters in hopes of identifying likely Obama supporters and tracking them through Election Day.